1. Field of the Invention
The present invention relates to a magnetic wire pulling system for use in routing electrical wires through walls; and more particularly to a method and means for the installation of new or additional telecommunication wires, optical cables or electrical wiring in difficult to access areas such as below floors, above ceilings, and within attics, walls and furred out columns in finished homes or office buildings, while minimizing the need for patch holes or cutting pathways in the sheetrock used to finish the wall.
2. Description of the Related Art
Installing electrical wiring behind walls, above ceilings, and beneath floors is a frustrating and potentially dangerous task for electricians as many times the installation requires the movement and positioning of wire through enclosed spaces that are inaccessible to human senses of touch and sight. Often, a wire must be fed through a first opening and then somehow caught by the electrician's fingers or with the electrician's pliers and pulled through a second opening. Inserting fingers into a dark enclosed space potentially containing nails, pipes, and other hazards may lead to injury. The presence of exposed electrical wiring within these spaces may result in extreme injury or even death when fingers or metallic pliers are used to catch the wire. Many times the path a wire must take from one opening to a second opening is blocked by a bearing member of the structure's frame such as joists within the ceiling or flooring as well as cripples within the walls. Moving a wire between joists or cripples in a finished structure is time consuming and requires additional patch holes to be created so the electrician has access to spaces that are completely enclosed.
A number of patent applications disclosing various systems have been filed with the object of facilitating the movement of wire from a first opening to a second opening through an enclosed space in a finished house or building. A sampling of related patent applications follows.
U.S. Pat. No. 3,078,073 to T. J. Zizzo discloses one such system. The electrical wire is attached to a conductor holder with a screwed fastener and inserted through a first wall opening for an electrical outlet. The top portion of the conductor holder carries a powerful permanent magnet. A flexible string is attached to a plumb bob, termed “sensor”, made from a magnetically attractable material such as steel is lowered from the attic in the same bay. When the sensor element comes in close proximity with the permanent magnet, it is attracted and is held securely by the permanent magnet. Pulling on the flexible string then drags the conductor holder upward within the bay. If excessive force is used during the lifting of the conductor holder, obstacles engage the conductor holder, or if the electrical wire attached to the conductor holder offers excessive resistance, the magnet force connecting the conductor holder to the sensor may be cancelled separating the conductor holder and sensor. Operational reliability thus presupposes lack of resistance of the wire to the pulling process, which is oftentimes not present during all installation conditions. In addition, this system is only useful in allowing an operator to position the line or wire from an upper location to a lower location as the flexible string has no structural rigidity.
U.S. Pat. No. 3,971,543 to Shanahan discloses system similar to the patent to Zizzo above. Disclosed is a device containing a chain formed from spherical elements connected by studs with a magnetically attractable body at one end of the chain and an eyelet at the opposing end of the chain. The chain can swing readily to contact a magnet. A flexible string is attached to the eyelet and the device is dropped into a bay within the wall. Meanwhile a magnet body is inserted into an opening in the wall that contains a magnet. As the device is lowered into the bay the chain may be swung about by a side to side movement by the electrician lowering the flexible string to facilitate connection if an offset exists from where the devices is dropped and the wall opening. When the magnetically attractable body at one end of the chain makes contact with the magnet body inserted through the wall opening the device may be pulled through the wall opening along with the flexible string. A wire may then be attached to the flexible string and pulled down to the wall opening or conversely up through the wall opening. The success of pulling a wire with the Shanahan system should be better than the Zizzo system as the attachment strength in Shanahan should be stronger than the attachment strength in Zizzo. However, obstacles may still prevent the lowering of the device moreover this system is only useful in allowing an operator to position the line or wire from an upper location to a lower location as the flexible string has no structural rigidity.
U.S. Pat. No. 4,527,775 to Flowers disclose a system for installing a conduit. A tape with a magnetically attractable roller is first inserted through an opening in an attic. The tape is guided to its destination behind a wall, using an electromagnet mounted on wheels, which rides on the interior wall. The electromagnet attracts the roller carrying the tape and guides it downward to its destination as the electromagnet is moved. Once the tape is brought through, a wire is firmly attached to the tape and is pulled up through the attic behind the wall. The electromagnet does not contact the interior wall, since it is riding on the rollers. As a result, the distance between the electromagnet and the magnetically attractable roller is larger than the thickness of sheetrock weakening the magnetic attraction between the electromagnet and the magnetically attractable roller. Any increase in this distance due to debris within the wall further reduces this magnetic attraction rendering the system unless. Moreover, the electromagnet requires a power source which may be difficult to obtain as electrical power is shutdown as a precaution to prevent injury to electricians. Finally, this system is not useful in applications where a joist or cripple blocks the path to be taken by the roller.
U.S. Pat. No. 5,522,630 to James discloses a fishing tool for magnetic objects. The tool consists of an electromagnet powered by a variable power DC battery source. In one embodiment, an electromagnet is attached to a string using an eyelet formed on the electromagnet. The assembly is lowered from an upper hole into a bay between joists disposed behind a sheetrock or plaster wall. A magnetizable fish tape is inserted in a lower hole in the same bay, and the electromagnet is energized using the variable DC power supply. The electromagnet attached to the string attracts and captures the fish tape. Each of the fish tape and the electromagnet is pulled through the lower hole, completing the string up operation. In a second embodiment, the fish tape is secured to a slot in the fishing tool, and is held by screws. The fishing tool, with the attached fish tape, is pushed up through the conduit from the lower hole and energized by the variable power DC source. A magnetizable fishing tape is inserted from the top to contact the energized fishing tool and capture it. The fishing tape together with the fishing tool is pulled through the upper hole. Both embodiments rely on a secure attachment between the energized electromagnet and magnetizable fish to complete the fishing operation. Since the electromagnet used in the first embodiment is heavy and carried by a flexible string, it can swing and may not easily contact the inserted fish tape at the lower hole, especially if the upper and lower holes are not aligned in a vertical plane. In the second embodiment, the heavy electromagnet is essentially carried by the fish tape, attached by screws in an asymmetric configuration, and has to carry the electrical leads. This configuration allows bending and collapse of the fish tape. It may not be inserted vertically, thereby impairing its ability to contact the inserted magnetizable fish tape at the upper hole. With either embodiment, the magnetizable object and the electromagnet must be in close proximity to create contact. In addition, the electromagnet must sustain the weight of the electromagnet and fish tape during pull. Such sustained contact is oftentimes not readily accomplished, and requires a high current that is not easily provided by a battery power source. Finally, as in the preceding disclosures, this system is not useful in applications where a joist or cripple blocks the path to be taken by the electromagnet.
U.S. Pat. No. 7,051,999 to Hewitt is similar to the Flowers patent except that rather than an electromagnet mounted on wheels Hewitt uses a permanent magnet coated with a low friction surface finish and rather than a magnetically attractable roller Hewitt uses a magnetic “mouse”. The magnetic mouse is dropped into a wall bay and driven by the permanent magnet to the desired wall opening. The magnetic mouse trails a string that is then used to pull a wire along the path followed by the magnetic mouse. By removing the wheels Hewitt is able to minimize the distance between the permanent magnet and the magnetic mouse. In addition, by using a permanent magnetic Hewitt's device does not require access to an electrical power source. However, there remains the problem of debris within the wall that may block the path to be taken by the magnetic mouse. Moreover, the permanent magnetic can be very expensive and its weight may make it difficult to drive the magnetic mouse across a ceiling. Finally, as in the preceding disclosures, this system is not useful in applications where a joist or cripple blocks the path to be taken by the magnetic mouse.
U.S. Pat. No. 7,093,822 to Welker discloses a variety of tools that may be used to guide a string from one opening to another. The tools comprise a retrieval tool, a manual release tool, an insertion tool, an automatic release tool, a transfer tool, an extensible prop, and a telescoping pole with magnet. The tools deliver a magnet into the structure of a house, retrieve a magnet from the structure, or transfer a magnet from one tool to another tool. The telescoping pole with magnet is the most similar tool to the present invention. The telescoping pole has a series of tubular sections with each section being of slightly smaller diameter than the previous section thus being able to slide into the previous section. The first and widest section contains a reel system whereon string may be collected. The string passes through each of the sections and is terminated by a magnet. The telescoping pole may be used to pull string above the ceiling, below the floor, and within the wall. The telescoping pole is fully extended and inserted into the first opening. Through the second opening a magnet with an eyelet is positioned and a string is attached to the eyelet. The magnet at the end of the telescoping pole makes contact with the magnet with the eyelet. The operator then pulls the magnet with the eyelet by use of the reel in the telescoping pole thereby drawing the string attached to the eyelet. The telescoping pole is a complex tool with many parts thus being prone to breakage. Moreover, as the distance to be covered from one opening to the other is great the pole, when fully extended, is unwieldy and subject to bending due to gravitational effects. The opening for the pole must be large to accommodate the length of the extended pole. Finally, when inserting the pole, if the tip of the pole encounters an obstacle then the sections of the pole will collapse one into another defeating the purpose of the pole especially when joists, cripples, or even weather insulation material is encountered by the pole.
The present invention solves a number of problems found in the prior art. The present invention is lightweight and of a simple design consisting of only a few parts and is very inexpensive to fabricate. This simple design makes the tool more durable and impervious to mechanical defects than the prior art due to the lack of mechanical members and connections such as a telescoping pole in Welker. Durability is a key factor to consider when pulling wires through existing construction due to the need of overcoming resistance forces and tolerating strong pulling and pushing forces. The present invention does not require any electrical power source and does not conduct electricity thereby protecting operators from electrical shock. The present invention may be used for drawing a pull string in horizontal as well as vertical applications. Finally, the present invention is designed to operate through small openings that are created in a joists, studs, top plates, fire blocks, or cripples.
The design also has measurement marking which allows for precise operation in unseen areas. The present invention does not require any electrical power source. The present invention may be used for drawing a pull string in horizontal as well as vertical applications. Also, the present tool is fully insulated to protect from electrical shock. Finally, the present invention is designed to operate through small openings that are created in a joists, studs, top plates, fire blocks, or cripples.